Method of mounting a plurality of electronic parts on a circuit board

ABSTRACT

An apparatus includes a connection sheet having a separator layer and an adhesive film layer formed on the separator layer such that said adhesive film layer can be peeled from the separator layer. The cohesive strength of the adhesive film layer decreases when the adhesive film layer is heated to a predetermined temperature. Electronic parts each have an electrode surface and at least one electrode on the electrode surface. The electrode surface of each of the electronic parts is affixed to the adhesive film layer such that the adhesive film layer coats all exposed portions of the electrode surface and coats all exposed surfaces of the at least one electrode

This application is a Divisional application of Ser. No. 08/907,017,filed Aug. 6, 1997 U.S. Pat. No. 6,158,115.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of mounting a plurality ofelectronic parts on a circuit board, and also to a method of producingadhesive-coated electronic parts suited for use in the mounting method.

2. Description of the Related Art

With a recent trend to smaller-sized, thinner electronic parts such assemiconductor chips (“electronic parts” referred to herein includeresistors, capacitors, semiconductor chips, etc. mounted on circuitboards), circuits and electrodes used in such electronic parts haveincreased density and finer connection pitch. Since fine electrodes aredifficult to connect by soldering, recently, connection methods usingadhesive are widely used. The connection methods include a method inwhich electrically conducting particles are mixed in an adhesive, andcontact bonding is performed to achieve electrical connection in thethickness direction of the adhesive (e.g., Unexamined Japanese PatentPublication (KOKAI) No. 55-104007). There is another and a method inwhich no conducting particles are contained in an adhesive, and contactbonding is performed to achieve electrical connection through directcontact of fine irregularities on the electrode surfaces (e.g.,Unexamined Japanese Patent Publication (KOKAI) No. 60-262430).

The connection methods using adhesive permit connection at relativelylow temperatures and also provide excellent reliability because theinterconnecting portion has flexibility. In addition, in the case whereadhesive formed into a film or tape is used, it is possible to supplythe adhesive of uniform thickness in the form of a long strip, wherebythe mounting line can be automated. Also, a simple step of applying heatand pressure simultaneously attains electrical connection betweenelectrodes of the semiconductor chip and the circuit board andmechanical connection of the two through bonding. This is why theconnection methods using adhesive are attracting attention.

In recent years, multi-chip modules (MCM) which employ a more elaborateform of the above methods and in which a large number of chips, aremounted at high density on circuit boards of relatively small size aredrawing attention. In general, an MCM is fabricated by forming anadhesive layer on a circuit board, peeling a separator, if any, from theadhesive layer, and positioning chips such that their electrodes facecorresponding electrodes on the circuit board, followed by bonding ofthe electrodes. Forming an adhesive layer on a chip instead presents theproblem that a complicated apparatus is required because a chip having asmaller area than the circuit board needs to be applied with an adhesivelayer.

Electronic parts used in MCM include a variety of chips such assemiconductor chips, active elements, passive elements, resistors andcapacitors.

Thus, various types of chips having different sizes (areas, heights) aremounted on MCM. When connecting chips to a circuit board, however, aproblem arises which is not associated with conventional techniques suchas the method of forming an adhesive layer on a circuit board or theheat-pressure bonding method.

Specifically, in the case where the adhesive used is in the form of afilm, adhesive strips (adhesive tapes) with different widths are neededdepending on different chip sizes. In MCM, however, multiple chips aremounted at high density on a small-sized circuit board, and thus only asmall mounting space is available, making it difficult to use a varietyof tape widths. Also, use of various tape widths increases the laborinvolved in the management of materials. Further, since differentdevices for feeding, contact bonding, tape rewinding, etc. are neededfor individual tape widths, the mounting apparatus is inevitablyincreased in overall size and is complicated, requiring a largeinstallation space and increasing the cost.

An attempt has therefore been made to mount various sizes of chips afteran adhesive layer is formed on the entire surface of a circuit board(Examined Japanese Patent Publication (KOKOKU) No. 61-27902). With thismethod, however, much labor is required to remove the remaining adhesivefrom non-connecting sections, and also the cost increases because theadhesive layer is formed uselessly on regions other than the mountingsections. Further, since the adhesive is applied to the entire surfaceof the circuit board, heat applied at the time of connection canadversely affect adjacent chip mounting sections. For example, thereaction of the thermosetting adhesive may progress to such an extentthat the adhesive on an adjacent section where a chip is not yet mountedbecomes unusable, or an adjacent chip may develop a connection defect asthe adhesive softens due to the connection heat even after the chip ismounted. This is also the case with removal of a defective chip afterchip mounting. Namely, it is difficult to peel off a defective chip andalso to remove the adhesive because of the reaction of the thermosettingadhesive.

Also, as an attempt to form an adhesive layer with a size substantiallyequal to the chip size, Examined Japanese Patent Publication (KOKOKU)No. 4-30742, for example, discloses forming an adhesive layer on a waferand then subjecting the wafer to full dicing. In this case also, varioustypes of adhesive-coated wafers must be prepared for different types ofchips, making the process control complicated in view of the shelfstability life of the adhesive.

Unexamined Japanese Patent Publications (KOKAI) No. 63-276237 and No.2-199847, for example, disclose applying an adhesive only to the topfaces of bump electrodes (also merely called bumps) on a chip, in orderto reduce the connectable pitch. However, since the adhesive is appliedonly to the top faces of the bump electrodes, the bump electrodes arebonded to a circuit board only in areas around the bump electrodes, sothat the bonding strength and the connection reliability are low. Inorder to also apply the adhesive to regions other than the top faces ofthe bump electrodes, an underfill material needs to be poured, which,however, complicates the process and increases the cost.

Further, in the case where chips with different heights are mounted orchips are mounted on both surfaces of a circuit board, heat and pressurecannot be uniformly applied by using conventional techniques generallyemployed, such as a press method in which a chip-carrying board isclamped by parallel mold elements or a pressure roll method usingparallel rolls. Thus it is impossible to connect fine electrodes in thissituation.

SUMMARY OF THE INVENTION

The present invention was created to eliminate the above-describeddrawbacks, and an object thereof is to provide a method of efficientlymounting electronic parts on a circuit board, groups of adhesive-coatedelectronic parts suited for use in the mounting method, and a method ofproducing adhesive-coated electronic parts.

According to a first aspect of the present invention, there is provideda method of mounting a plurality of electronic parts on a circuit boardby bonding and fixing electrodes of the electronic parts to the circuitboard to electrically connect the individual electronic parts to thecircuit board. The method comprises: an adhesive layer formation step offorming, on an electrode surface of each of the electronic parts onwhich the electrodes are formed, a film-like thermosetting adhesivelayer having an area substantially equal to that of the correspondingelectrode surface, to obtain adhesive-coated electronic parts; apositioning step of arranging the electrodes (on which the adhesivelayer is formed) so as to face corresponding electrodes of the circuitboard and positioning the electrodes relative to each other; and aheat-pressure bonding step of applying heat and pressure to theelectrodes of the electronic parts and the electrodes of the circuitboard to fix the electrodes to each other after the electrodes arepositioned.

According to the first aspect of the invention, the adhesive layer isformed beforehand on the electrode surface of each electronic part theelectrode surface thus applied with the adhesive is affixed tocorresponding electrodes on the circuit board, so that almost noadhesive superfluously comes out of the electrode surfaces. Accordingly,when mounting the electronic parts on the circuit board, it isunnecessary to remove superfluous adhesive, unlike the conventionalprocess, whereby the efficiency is improved and the cost can be reduced.

The electrodes are bonded to the circuit board with heat and pressureapplied thereto after the electrodes are set in position, and therefore,the electrodes can be shifted as needed and thus can be positioned withaccuracy. Even in the case where electronic parts with different heightsor sizes are mounted, the electrodes of the electronic parts areindividually fixed with heat and pressure applied thereto, whereby theelectrodes can be applied uniformly with heat and pressure and theelectronic parts can be easily mounted with reliability. In particular,it is possible to connect fine electrodes.

Preferably, the area of the film-like adhesive layer falls within arange of ±30% with respect to the area of the electrode surface of thecorresponding electronic part. If the area of the adhesive layer isgreater than the ±30% range, too much adhesive comes out of theelectrode surfaces, possibly requiring the adhesive removing step; onthe other hand, if the area of the adhesive layer is smaller than the±30% range, then there is the possibility of the electronic partsfailing to be satisfactorily connected.

The electronic parts are preferably held by a heating head by means ofsuction, for example, so that the surfaces of the electronic parts canbe heated by the heating head. The heating head serves to locate theelectronic parts in predetermined position while holding the same, andthen to immediately heat the electronic parts to be bonded and fixed tothe circuit board. Thus the apparatus and the process can be simplified.

The heat-pressure bonding step preferably includes an inspection step ofinspecting the electrical connection between the electrodes while thecohesive strength of the adhesive is increased to such an extent thatthe connection of the electrodes can be maintained. Namely, while theelectronic parts are temporarily fixed with the cohesive force of theadhesive increased, the electrical connection is inspected. Even in thecase where defective connection is discovered, repair work can be easilycarried out because the electronic parts are fixed only temporarily.

According to a second aspect of the present invention, there is provideda method of mounting a plurality of electronic parts on a circuit boardby bonding and fixing electrodes of the electronic parts to the circuitboard to electrically connect the individual electronic parts to thecircuit board. The method comprises: an adhesive layer formation step offorming, on an electrode surface of each of the electronic parts onwhich the electrodes are formed, a film-like thermosetting adhesivelayer having an area substantially equal to that of the correspondingelectrode surface, to obtain adhesive-coated electronic parts; atemporary fixing step of positioning the electrodes of the electronicparts (on which the adhesive layer is formed) so as to facecorresponding electrodes of the circuit board, and increasing cohesivestrength of the adhesive to such an extent that connection of theelectrodes can be maintained; and a heat-pressure bonding step ofapplying heat and pressure to the temporarily fixed electrodes to fixthe electrodes to each other, the heat-pressure bonding step includingsimultaneously heating a plurality of electronic parts in an autoclavewith a static pressure applied thereto within the autoclave.

According to the second aspect of the invention, in the heat-pressurebonding step according to the first aspect of the invention, a pluralityof electronic parts are simultaneously heated in the autoclave under thestatic pressure within the autoclave. Thus multiple electronic parts canbe easily bonded and fixed at one time with a simple arrangement.

Also in the second aspect of the invention, the area of the film-likeadhesive layer preferably falls within a range of ±30% with respect tothe area of the electrode surface of the corresponding electronic part,as mentioned above.

Further, the heat-pressure bonding step preferably includes aninspection step of inspecting the electrical connection between theelectrodes while the cohesive strength of the adhesive is increased tosuch an extent that the connection of the electrodes can be maintained.Namely, while the electronic parts are temporarily fixed with thecohesive strength of the adhesive increased, the electrical connectionis inspected. Even in the case where a defective connection isdiscovered, repair work can be easily carried out because the electronicparts are fixed only temporarily.

According to a third aspect of the present invention, there is provideda group of adhesive-coated electronic parts each having an electrodesurface coated with a film-like adhesive layer. The adhesive-coatedelectronic part group comprises: a connection sheet including afilm-like adhesive layer and a separator from which the film-likeadhesive layer can be peeled; and a plurality of electronic partsarranged on the film-like adhesive layer of the connection sheet, eachof the electronic parts being affixed to the adhesive layer at anelectrode surface thereof.

According to the third aspect of the invention, a plurality ofelectronic parts are affixed to the adhesive film. Therefore, when theelectronic parts are used, they are peeled off the separator film ispeeled off, so that the electrode surface of each electronic part iscoated with the adhesive layer. Namely, adhesive-coated electronic partscan be readily obtained, and in the case where electronic parts aremounted on circuit boards, a connection sheet with electronic partsaffixed thereon is prepared and the electronic parts are peeled off ofthe connection sheet, thereby obtaining adhesive-coated electronic partsready for use. Consequently, the process control of the mounting processis facilitated, and also the adhesive-coated electronic parts haveexcellent shelf stability.

Preferably, the adhesive layer contains electrically conductingparticles. The conducting particles serve to electrically connectelectrodes facing each other with reliability and also to insulateadjacent electrodes from each other.

According to a fourth aspect of the present invention, there is provideda method of producing an adhesive-coated electronic part having anelectrode surface coated with a film-like adhesive layer. The methodcomprising a connection sheet placement step of arranging a connectionsheet including a film-like adhesive layer and a separator from whichthe adhesive layer can be peeled, the connection sheet having a sizegreater than that of an electrode surface of an electronic part on whichelectrodes are formed; a contacting step of bringing the electrodesurface of the electronic part into contact with the adhesive layer; aheating step of heating the electrode surface to form a cohesionreduction line at which cohesive strength of the adhesive lowers, at alocation between a region of the adhesive layer corresponding to theelectrode surface and a region of the adhesive layer surrounding theelectrode surface; and a separating step of separating the electronicpart from the connection sheet such that part of the adhesive layerhaving a size substantially identical with that of the electrode surfaceis separated from the separator and adheres to the electrode surface.

According to the fourth aspect of the invention, the electrode surfaceof the electronic part is brought into contact with the connectionsheet, and the electrodes are heated so that the cohesive strength ofthe adhesive around the electrodes may lower. Namely, the adhesive setswith a certain cohesive strength at normal temperature, but the cohesivestrength lowers (or the adhesive softens) when the adhesive is heated upto a predetermined temperature. Accordingly, when the electronic part isseparated from the connection sheet, part of the adhesive layercorresponding in size to the periphery of the electrode surfaceseparates from the separator and adheres to the electrode surface, thuseasily obtaining an adhesive-coated electronic part which is coated withan adhesive layer having a size substantially equal to that of theelectrode surface.

The cohesion reduction line is formed along the periphery of theelectrode surface and is the boundary between a region of the adhesivelayer where the cohesive strength lowers when the electrodes are heatedand a region of the adhesive layer where the cohesive strength remainsalmost the same. In the case of adhesive, cohesive property is differentfrom setting or hardening property (activation). Thus the former term isapplicable to both thermosetting adhesive and heat softening adhesive.

According to a fifth aspect of the invention, there is provided a methodof producing an adhesive-coated electronic part having an electrodesurface coated with a film-like adhesive layer. The method comprises: aconnection sheet placement step of arranging a connection sheetincluding a film-like adhesive layer and a separator from which theadhesive layer can be peeled, the connection sheet having a size greaterthan that of an electronic part; a contacting step of bringing anelectrode surface of the electronic part on which electrodes are formedinto contact with the adhesive layer; a cutting step of pressing theelectrode surface against the adhesive layer and cutting at least partof the adhesive layer along a periphery of the electronic part; and aseparating step of separating the electronic part from the connectionsheet such that part of the adhesive layer is separated from theseparator and adheres to the electrodes.

According to the fifth aspect of the invention, the electrode surface ofthe electronic part is pressed against the adhesive layer of theconnection sheet, and the adhesive layer is cut along the electrodesurface (electronic part) to thereby separate part of the adhesive layerwhich is in contact with the electrode surface from the other part ofthe adhesive layer. Consequently, it is possible to easily obtain withreliability an adhesive layer having a size substantially identical tothat of the electrode surface of the electronic part.

Preferably, the cutting step is achieved using a cutter arranged at apressure head for pressing the electrodes of the electronic part againstthe connection sheet, or using a heating wire. Using the cutter arrangedat the pressure head or the heating wire makes it possible to easilyobtain an adhesive layer having a size substantially equal to that ofthe electronic part or the electrode surface.

Preferably, the connection sheet is placed on a surface plate with acushioning member interposed therebetween. In this case, the impact atthe time of application of pressure by the pressure head or at the timeof cutting can be absorbed.

Further, the adhesive layer preferably contains electrically conductingparticles in order to enhance the insulating property of an electrodefrom adjacent electrodes, as mentioned above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic sectional views illustrating the processof a mounting method according to the present invention;

FIGS. 2A, 2B and 2C are plan views showing the width of an adhesivestrip and exemplary arrangements of chips according to the presentinvention;

FIG. 3 is a schematic sectional view illustrating another embodiment ofthe present invention;

FIG. 4 is a schematic sectional view illustrating still anotherembodiment of the present invention;

FIGS. 5A through 5D are schematic sectional views showing the structuresof adhesive-coated chips according to the present invention;

FIGS. 6A, 6B and 6C are schematic sectional views showing other examplesof adhesive-coated chips according to the present invention;

FIGS. 7A and 7B are schematic sectional views showing the arrangementsof adhesive-coated chip groups according to the present invention; and

FIG. 8 is a perspective view of an MCM on which adhesive-coated chipsaccording to the present invention are mounted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be hereinafter described with reference tothe drawings illustrating embodiments thereof.

FIG. 1 schematically illustrates, in section, an embodiment of thepresent invention. FIG. 1A shows part of a heat-pressure bondingapparatus used in a mounting method according to the present invention.An adhesive tape 6 consisting of an adhesive layer 4 and a separator 5is arranged between a heating head 2, which is capable of fixing a chip1 thereon by, for example, suction, and a surface plate 3. The adhesivelayer 4 is positioned so as to face an electrode surface of the chip(semiconductor chip) 1 as an electronic part. The electronic part usedin this case may be an element other than the semiconductor chip, suchas an active element, a passive element, a resistor or a capacitor.

The adhesive tape 6 is brought into close contact with the surface plate3 by, for example suction. Alternatively, it may be allowed to travelwhile being kept taut by rolls or the like (not shown) arranged in frontand at the rear of the surface plate 3, respectively. The adhesive layer4 can be peeled from the separator 5. Since the separator 5 is in closecontact with or kept taut on the surface plate 3, the separation of theadhesive layer 4 from the separator 5 is facilitated.

Pressure is developed between the heating head 2 and the surface plate3, whereupon the electrode surface of the semiconductor chip 1, on whichelectrodes are formed, is brought into contact with the adhesive layer 4having a greater area than the electrode surface. The adhesive layer 4preferably has a size corresponding to the largest size of multiplechips to be mounted on an MCM so that the adhesive layer 4 can be usedfor other chips as well and can be handled with ease. In this case, thesize of the adhesive layer 4 is selected so as to correspond to theshorter side of the chip with the largest size, whereby the width of theadhesive tape can be narrowed and the installation space for theapparatus can advantageously be reduced.

The width of the adhesive layer 4 (more generally, the width of theadhesive tape) may be substantially equal to the shorter side of thechip as shown in FIG. 2A, or may be slightly greater than the shorterside of the chip as shown in FIG. 2B. Alternatively, the adhesive layer4 may have such a size that two chips can be arranged in the widthdirection of the adhesive layer 4, as shown in FIG. 2C. Any of thesetape widths may be selected taking account of handling andmass-productivity.

Referring again to FIG. 1A, the heating head 2 is heated up to apredetermined temperature to directly heat a back surface of the chip 1which is opposite the electrode surface, so that a region of theadhesive layer corresponding to the chip size is preferentially heated.During the heating, a region of the adhesive surrounding the chip 1 isscarcely heated and maintains the form of a film because the adhesivehas low heat conductivity and thus little heat is transmitted to thesurrounding region. On the other hand, a region of the adhesive layer 4which is in close contact with the chip 1 adheres fast to the chip 1 asthe viscosity lowers, or tackiness increases, due to the application ofheat, thus increasing the film strength. Consequently, a cohesionreduction line across which the cohesive strength of the adhesive layer4 lowers is formed along the periphery of the chip 1.

The heating temperature of the head 2 is set to a temperature at whichthe adhesive layer 4 softens and melts (its viscosity is preferably 1000poises or less, more preferably 100 to 10 poises) and at the same timethe hardening reaction of the adhesive is not initiated or at a lowlevel (the rate of reaction is 20% or less), and is selectedappropriately depending on the type of adhesive used. Further, the head2 is preferably heated at a temperature lower than or equal to theactivation temperature of a latent hardener, mentioned later, in orderto improve the shelf stability of adhesive-coated chips.

FIG. 1B shows a state in which the heating head 2 is moved away from thesurface plate 3, and as illustrated, part of the adhesive layer 4substantially equal in size to the chip 1 can be separated along thecohesion reduction line of the adhesive layer corresponding to theperiphery of the chip 1 and adhere to the chip 1. Although the adhesivelayer 4 on the surface plate 3 has an adhesive-free region from whichadhesive has been transferred to the chip 1, the adhesive tape 6maintains the form of a film because of the presence of the separator 5and the remaining adhesive 4. Adhesive can be set on the surface plate 3by removing the adhesive-free region or by moving the adhesive tape 6.

In the case shown in FIGS. 1A and 1B, an adhesive-coated chip to whichthe adhesive layer 4 has been transferred from the separator 5 isobtained. Thus the adhesive-coated chip can be directly connected to acircuit board, permitting continuous fabrication of MCM. When keepingthe adhesive tape in stock, a separator may be affixed to the adhesivelayer. In the arrangement of FIGS. 1A and 1B, various chips may beplaced beforehand on the tape so that adhesive-coated chips can beefficiently obtained by removing the chips from the tape. In this case,a variety of adhesive-coated chips can be continuously fed in desiredorder, thus improving the productivity.

FIG. 3 is a schematic sectional view showing the manner of obtaining anadhesive-coated chip according to another embodiment of the presentinvention. FIG. 3 shows part of a pressure bonding apparatus, and anadhesive tape 6 consisting of an adhesive layer 4 and a separator 5 isplaced between a pressure head 8, to which a chip 1 is fixed by suction,for example, and a surface plate 3. The adhesive tape 6 is brought intoclose contact with the surface plate 3 by suction, for example.Alternatively, the adhesive tape 6 may be allowed to travel while beingkept taut by rolls or the like (not shown) arranged in front and at therear of the surface plate 3, respectively.

The pressure head 8 is provided with a cutting jig 7. The cutting jig 7has an edge extending along the periphery of the chip 1; in the casewhere the size of the chip in the width direction of the adhesive tapeis substantially equal to the tape width, the cutting jig 7 may have twostraight edges extending across the tape width. The adhesive layer 4 iscut by the cutting jig 7 in the thickness direction for at least a partor the whole of the depth thereof, thereby allowing part of the adhesivelayer 4 with a size substantially equal to the chip size to adhere tothe chip 1. At this time, the pressure head 8 may not be heated, inwhich case the fabrication work can be performed at room temperatures,making it possible to prevent the adhesive from being adversely affectedby heat. A razor made of metal, ceramic, etc., or energy rays such asheat, ultraviolet radiation, laser beam, etc. can be used as the cuttingjig 7.

In the case where a cutting tool is used as the cutting jig 7 and theadhesive layer is cut by pressing the cutting jig 7 downward, the heightof the cutting jig 7 (that is, the distance from the connection surfaceof the chip 1) is determined taking account of the depth to which theadhesive layer 4, or both the adhesive layer 4 and the separator 5, areto be cut. The adhesive layer 4 is preferably cut for its whole depth inview of ease of separation of the adhesive-coated chip from the tape.The cutting jig 7 may in this case comprise a vertically movablemechanism which can be contained in the pressure head 8 so thatcontinuous production efficiency can be enhanced.

In the arrangement shown in FIGS. 1A and 1B or in FIG. 3, a cushioninglayer 11 made of rubber or the like may be interposed between thesurface plate 3 and the separator 5, as shown in FIG. 4. In this case, achip coated with adhesive corresponding in size to the periphery of thechip can advantageously be obtained with ease.

Various examples of adhesive-coated chips obtained in theabove-described manner will be now explained with reference to FIGS. 5Ato 5D and FIGS. 6A to 6C. In all examples described below, the electrodesurface of the chip 1 is covered on its entirety with an adhesive filmhaving an area substantially corresponding to the chip size.

FIG. 5A illustrates a basic structure of the adhesive-coated chip, inwhich the semiconductor chip 1 and the adhesive layer 4 are of asubstantially identical size. FIGS. 5B and 5C illustrate cases where thesize of the adhesive layer 4 is made somewhat different from that of thesemiconductor chip 1 for adjustment of the optimum amount of adhesiveafter the connection to a circuit board. The size of the adhesive layerpreferably falls within a range of about ±30% with respect to the chipsize in view of the shape stability of the adhesive-coated chip, andmore preferably, the adhesive layer should be identical in size with thesemiconductor chip. In the present invention, the sizes of the adhesivelayers shown in FIGS. 5A to 5C are regarded as substantially identicalwith the size of the semiconductor chip. FIG. 5D illustrates the casewhere the separator 5 remains affixed to the adhesive layer 4, in whichcase dust or the like can advantageously be prevented from adhering tothe adhesive layer while the semiconductor chip is kept in stock.

FIGS. 6A and 6B illustrate the cases where the chip has bump electrodes12, and FIG. 6C illustrates the case where the chip has a wiring layer13 instead of pump electrodes. In FIGS. 6A and 6B, the adhesive containselectrically conducting particles 14, and in FIG. 6C, the adhesivecontains no conducting particles. The structures shown in FIGS. 6A to 6Ccan be combined in desired manner in respect of bump electrodes andpresence/absence of conducting particles. Furthermore, as shown in FIGS.5A-5D and FIGS. 6A-6C, the entire electrode surface of each chip(electronic part) 1, as well as all exposed surfaces of bump electrode12, are covered by the adhesive layer 4.

FIG. 7A illustrates a group of adhesive-coated chips, wherein aplurality of chips are placed separately on the separator with theirentire electrode surfaces covered with adhesive films of substantiallyidentical size. The tape with the chips affixed thereon can be rolledup.

As shown in FIG. 7B, adhesive films 4 a, 4 b and 4 c corresponding insize to respective chips may be present only on regions of the separator5 where the chips are separately affixed. In this case, by arrangingvarious chips on the separator in order of mounting on a circuit board,for example, it is possible to continuously feed adhesive-coated chipsin order, thus enhancing the productivity.

The adhesive-coated chips obtained in the above-described manner may beused for single-chip mounting, and also for multi-chip mounting asdescribed below.

First, using a microscope or an image storage device, the electrodes ofeach adhesive-coated chip are positioned accurately with respect tocorresponding electrodes on a circuit board. For the positioning,registration marks may also be used. Subsequently, the electrodes to beconnected to each other are applied with heat and pressure, so thatmultiple chips are electrically connected to a single circuit board. Inthis case, heat and pressure may be applied to one chip at a time, butif multiple chips can be bonded at the same time, the productivity isgreatly enhanced.

To apply heat and pressure, besides an ordinary press method, a staticpressure method using an autoclave etc. may be used whereby chips withdifferent thicknesses or sizes can be applied uniformly with heat andpressure. The static pressure mentioned herein denotes a constantpressure acting perpendicularly on the surface of an object. In general,the chip is 2 to 20 mm square, whereas the interconnecting section is 1mm or less, in many cases 0.1 mm or less, in thickness and thus is byfar smaller than the chip area, permitting a sufficient pressure to actin the direction of connection of the electrodes.

During the application of heat and pressure, continuity test may beconducted to examine the electrical connection between electrodes to beconnected to each other. Since continuity test can be performed whilethe adhesive is not set at all or is insufficiently set, repair work isfacilitated. Preferably, the test is conducted when the rate of reactionof the adhesive is about 30% or less, in order to facilitate repair workusing solvent. Where the rate of reaction of the adhesive is lower than10%, pressure is preferably applied since the fixing of the electrodesis not firm enough.

In this manner, a plurality of chips 1 with different shapes or sizesare mounted on a circuit board 9 via the adhesive layer 4, as shown inFIG. 8, thereby obtaining a multi-chip module (MCM) in which chips aremounted at high density on the circuit board 9 of relatively small size.The circuit board 9 to which the present invention can be appliedincludes, for example, a plastic film of polyimide, polyester, etc., acomposite material such as a glass fiber-epoxy composite material, asemiconductor of silicon etc., and an inorganic substrate of glass,ceramic, etc.

For the adhesive layer 4 used in the present invention, thermoplasticmaterials and various other materials which set upon receiving heat orlight can be used. Preferably, those materials which set upon receivingheat or light are used since they exhibit excellent heat resistance andhumidity resistance after the connection. Among these, an epoxy adhesivecontaining a latent hardener and an acrylic adhesive containing aradical hardener such as peroxide are especially preferred because theyset in a short period of time, can improve the efficiency of theconnection work, and have excellent adhesive properties due to theirmolecular structure. The latent hardener has a relatively distinctactivation point at which heat- or pressure-induced reaction starts, andthus is suited for the present invention involving the heat/pressureapplication step.

As the latent hardener, imidazole, hydrazide, boron trifluoride-aminecomplex, amine-imide, polyamine salt, onium salt, dicyandiamide, andmodified substances thereof maybe used singly or in combination to forma mixture.

These are catalytic hardeners of ionic polymerization type such asanionic or cationic polymerization type, and are preferred because theycan set rapidly and because no special attention needs to be paid tochemical equivalents. Among the catalytic hardeners, an imidazolehardener is especially preferred since it is non-metallic and thus isless susceptible to electrolytic

corrosion. The imidazole hardener is also used in view of reactivity andconnection reliability. Further, other hardeners such as a polyaminehardener, a polymercaptan hardener, a polyphenol hardener and an acidanhydride hardener can be used, and also these hardeners may be used incombination with the aforementioned catalytic hardeners. Amicro-encapsulated hardener in which the hardener as a core material iscovered with a polymeric substance or an inorganic substance is alsopreferred because of its opposing properties, that is, long-term shelfstability and rapid setting property.

The hardener for the adhesive used in the present invention shouldpreferably have an activation temperature of 40 to 200° C. If theactivation temperature is lower than 40° C., the difference between theactivation temperature and room temperature is so small that theadhesive needs to be kept at low temperature. If the activationtemperature is higher than 200° C., other chips and the like areadversely affected by heat during the connection. For this reason, theactivation temperature should preferably fall within a range of 50 to150° C. The activation temperature mentioned herein represents anexothermic peak temperature of a compound of epoxy resin and thehardener, as a sample, which is measured by using a DSC (differentialscanning calorimeter) while the sample is heated from room temperatureat a rate of 10° C./min. With low activation temperature, goodreactivity is achieved but the shelf stability tends to lower, andtherefore, suitable activation temperature is selected taking this intoconsideration. According to the present invention, the shelf stabilityof adhesive-coated chips is improved by carrying out heat treatment at atemperature lower than or equal to the activation temperature of thehardener, and excellent multi-chip connection is achieved at atemperature higher than or equal to the activation temperature.Preferably, therefore, the melt viscosity of the adhesive is adjustedsuch that the aforementioned cohesion reduction line is formed at atemperature lower than or equal to the activation temperature of thehardener.

The adhesive layer 4 is preferably admixed with electrically conductingparticles 14 or with a small quantity of insulating particles (notshown), since the particles serve to maintain the layer thickness at thetime of application of heat and pressure during the fabrication ofadhesive-coated chips. The proportion of the conducting or insulatingparticles admixed in this case is approximately 0.1 to 30 vol %, and isset to 0.5 to 15 vol % in order to obtain anisotropic conductivity. Theadhesive layer 4 may alternatively have a multi-layer structureincluding an insulating layer and an electrically conducting layerformed separately from each other. In this case, resolution improves,permitting high-density connection of electrodes.

The electrically conducting particles 14 may be metal particles of Au,Ag, Pt, Co, Ni, Cu, W, Sb, Sn or solder, or particles of carbon,graphite, etc. Further, such conducting particles or nonconductiveparticles, such as glass particles, ceramic particles or polymericparticles of plastic, may be used as cores, which are then coated withan electrically conductive layer using one of the above substances.Also, insulator-coated particles having electrically conducting corescoated with an insulating layer, or the combination of conductingparticles and insulating particles of glass, ceramic or plastic may beused to improve the resolution.

In order that one or more electrically conducting particles, preferablyas many particles as possible, will be present on each fine electrode,the particle size of the conducting particles 14 should preferably be assmall as 15 μm or less and, more preferably, in the range of 7 to 1 μm.If the particle size is smaller than 1 μm, difficulty arises in makingthe particles in contact with the electrode surfaces. Also, theconducting particles 14 should preferably be uniform in particle size,because uniform particle size serves to lessen the outflow of conductingparticles from between electrodes facing each other.

Among the aforementioned electrically conducting particles, particleshaving polymeric cores of plastic material coated with a conductivelayer and particles of heat-fusible metal such as solder are preferablyused, because these particles deform when applied with pressure or bothheat and pressure, so that the area of contact with circuits increases,thus improving the reliability. In particular, in the case wherepolymeric cores are used, the particles do not show such a distinctmelting point as that of solder. Thus the softened state canadvantageously be controlled over a wide range of connectiontemperatures and variations in the thickness or flatness of electrodescan be easily coped with.

Where hard metal particles of Ni or W, for example, or particles havinga large number of protuberances on their surface are used, theconducting particles stick into the electrodes or wiring patterns. Thuslow connection resistance is achieved even if an oxide film or acontamination layer exists on the electrode surface, whereby thereliability can be improved.

With the multi-chip mounting method according to the present invention,adhesive-coated chips of different sizes can be mounted as needed on acircuit board, thereby facilitating the mounting of a large number ofchips on a circuit board with a small area.

According to the present invention, since chips coated with respectiverequired amounts of adhesive are used, the number of tapes withdifferent widths may be small and the mounting apparatus can besimplified, as compared with the case of using different adhesive tapesfor different sizes of chips. Further, unlike the case where an adhesivelayer is formed over the entire surface of a circuit board, neitheradjacent chips nor surrounding adhesive is adversely affected by heat orpressure, and no extra adhesive is used, which is advantageous from theeconomical viewpoint.

In the preferred embodiment of the present invention, the adhesivecontains a latent hardener, and heat treatment is performed at atemperature lower than or equal to the activation temperature of thehardener to obtain adhesive-coated chips. Accordingly, the shelfstability of the adhesive is improved, and a reliable multi-chipconnection can be achieved at a temperature higher than or equal to theactivation temperature.

With the multi-chip mounting method of the invention using hydrostaticpressure, the pressure within the airtight vessel is kept constant, anda large number of MCM can be treated at the same time, whereby the massproduction efficiency is enhanced. Also, since the heat treatment iscarried out using gas or liquid as the medium, it is unnecessary to useexpensive molds, and various adhesives having different properties inrespect of heat, humidity and anaerobic characteristic can be useddepending on the type of medium used. Further, even if the adhesivetakes a long time to set, it is possible to produce a large number ofMCM by one operation.

According to the multi-chip mounting method of the present invention, acontinuity test can be performed before the adhesive finally sets.Therefore, when a defective connection is discovered, the adhesive isthen still not sufficiently set, and thus the peeling of chips and thesubsequent cleaning operation using a solvent such as acetone can becarried out very easily, thereby facilitating the repair work.

Also, by arranging groups of adhesive-coated chips on the separator inorder of mounting on circuit boards, it is possible to improve theproductivity.

In the method of producing adhesive-coated chips according to thepresent invention, a cohesion reduction line is readily formed in theadhesive layer around the chip when the chip is heated. Since theadhesive layer can be peeled from the separator, a chip coated with anadhesive layer having a size corresponding to the chip size can beobtained relatively easily. By setting the heating temperature at atemperature lower than or equal to the activation temperature of thehardener, the adhesive-coated chips can be kept for later use withoutlowering their shelf stability.

According to the adhesive-coated chip production method of the presentinvention, the adhesive layer is cut for at least part of its depth inthe thickness direction by using a very simple cutting jig matching thechip shape, so that a chip coated with an adhesive layer having a sizecorresponding to the chip size can be obtained relatively easily.

EXAMPLES

Various examples according to the present invention are described indetail below, but it should be noted that the present invention is notlimited to these examples alone.

Example 1

(1) Preparation of Adhesive Layer

A solution containing 30% of ethyl acetate was obtained by mixing, inthe ratio of 30/70, a phenoxy resin (polymeric epoxy resin) and a liquidepoxy resin (epoxy equivalent: 185) containing a micro-encapsulatedlatent hardener. To this solution was added 2 vol % of electricallyconducting particles, which were obtained by coating polystyreneparticles having a particle size of 3±0.2 μm with Ni and Au inthicknesses of 0.2 μm and 0.02 μm, respectively, followed by mixing anddispersion of the conducting particles. The dispersion was applied to aseparator (polyethylene terephthalate film treated with silicone;thickness: 40 μm) by means of a roll coater, and the separator appliedwith the dispersion was dried at 100° C. for 20 minutes to obtain anadhesive film with a thickness of 20 μm.

The activation temperature of the adhesive film was measured using a DSCand was found to be 120° C. Using a model composition from which thehardener had been removed, the viscosity of the adhesive layer wasmeasured by a digital viscometer HV-8 (manufactured by Kabushiki KaishaReska), and was 800 poises at 100° C.

The adhesive film was cut together with the separator to obtain a tapeof 2 mm wide.

(2) Fabrication of Adhesive-coated Chip

The tape obtained in the manner described in (1) above was set in a chipmounting apparatus AC-SC450B (COB connecting apparatus manufactured byHitachi Chemical Co., Ltd.) with its adhesive layer facing upward, andwas held tense by rolls arranged in the front and at the rear of thesurface plate in such a manner that the tape could travel in closecontact with the surface plate. An IC chip for evaluation (2×10 mmsilicon substrate having a thickness of 0.5 mm and having 300 goldelectrodes (called bumps) of 50 μm in diameter and 20 μm high formednear the two longer sides of the substrate) was fixed to the heatinghead in position by suction.

With the temperature of the heating head set at 110° C., the tape wassubjected to heat-pressure bonding such that its adhesive layer wasapplied with 5 kg/cm² for 3 seconds, and then the heating head wasraised to release the tape from pressure and separated from the surfaceplate. The actual temperature of the adhesive of the tape in contactwith the surface of the IC chip was in this case 102° C. at the maximum.In this manner, an adhesive-coated chip with an adhesive layer, whichhad been separated from the separator and had a size nearly identical tothe chip size, was obtained.

Two 5×5 mm IC chips (tape width: 5.5 mm) and one IC chip of 10 mm indiameter (tape width: 10.5 mm) were prepared in a like manner, therebyobtaining a total of four adhesive-coated chips. These chips haddifferent bump pitches, but had the same bump height and the samesilicon substrate thickness.

(3) Connection On a 15×25 mm glass epoxy substrate (FR-4 grade) whichhad a thickness of 0.8 mm, had copper circuits of 18 μm high thereon,and had connection electrodes formed at terminals of the circuits atpitches corresponding to the bump pitches of the respective IC chipsobtained in the manner described in (2) above, the adhesive-coated ICchips were arranged. After the electrodes were positioned relative toeach other using a CCD camera, the chips were collectively connected at150° C. under 20 kgf/mm² for 15 seconds. Consequently, an MCM with fouradhesive-coated chips of substantially equal height collectively mountedthereon was obtained. At the time of the connection, aPolytetrafluoroethlene sheet of 100 μm thick was interposed as abuffering member between the chips and the heating head.

(4) Evaluation

The electrodes of the individual chips could be satisfactorily connectedto the corresponding electrodes on the substrate. Since the adhesive waspresent only in the vicinity of the chips, almost no superfluousadhesive could be observed on the surface of the substrate. Further, oneMCM could be obtained within one minute.

Example 2

IC chips were mounted on a substrate in substantially the same manner asin Example 1, but the adhesive-coated chips were produced by a differentmethod. Specifically, a pressure head provided with a cutting jig wasused, and the tape used had a width of 10 mm. For the 2×10 mm chip, forexample, a heater wire comprising a nichrome wire and arranged so as toextend along the four sides of the chip was used as the cutting jig. Thepressure head was not heated and was used at room temperature. Since aheater wire was used as the cutting jig, the tape could be cut for theentire depth inclusive of the separator, so that an adhesive-coated chiphaving a separator affixed to its adhesive layer was obtained. Otherchips could also be similarly affixed with adhesive. For the chip of 10mm in diameter, a looped heater wire with an inner diameter of 11 mm wasused as the cutting jig. Also in this case, the electrodes of theindividual chips could be satisfactorily connected to the correspondingelectrodes on the substrate. Since the adhesive was present only in thevicinity of the chips, almost no superfluous adhesive could be observedon the surface of the substrate.

Example 3

IC chips were mounted on a substrate in substantially the same manner asin Example 2, but when producing adhesive-coated chips, the temperatureof the heating head was set at 70° C. Further, a cutting tool with astraight edge was used as the razor. Also in this case, adhesive-coatedchips could be easily obtained. Since both the razor and the heatingmeans were used, the adhesive could be readily transferred to the chips.Furthermore, the heating temperature could be set at a low temperature,as compared with the case of Example 1.

Example 4

IC chips were mounted on a substrate in substantially the same manner asin Example 1, but the adhesive-coated chips were producing by adifferent method. Specifically, various chips were temporarily fixed (byheat-pressure bonding at 100° C. under 5 kg/cm² for 3 seconds)beforehand on a tape (width: 10.5 mm) so that the chips could becontinuously fed in order, as shown in FIG. 7A, and adhesive-coatedchips each with an adhesive layer, which had been separated from theseparator and had a size nearly identical to the corresponding chipsize, were obtained in the same manner as in Example 1. In this case,the adhesive could be easily peeled from the separator, and since thechips were prepared in order of mounting, the productivity was extremelyhigh. The electrodes of the individual chips could be satisfactorilyconnected to the corresponding electrodes on the substrate.

Example 5

Adhesive-coated chips obtained in the same manner as in Example 4 wereagain temporarily fixed on a continuous separator at intervals of 1 mmbetween adjacent chips, to obtain a series of adhesive-coated chips asshown in FIG. 7B. The productivity was extremely high because the chipscould be removed from the separator in mounting order. The electrodes ofthe individual chips could be satisfactorily connected to thecorresponding electrodes on the substrate. Also, since the series ofadhesive-coated chips could be wound on a reel with an outside diameterof 55 mm into a compact size, the chips could be easily kept in coldstorage after operation. The electrodes of the individual chips could besatisfactorily connected to the corresponding electrodes on thesubstrate.

Example 6

IC chips were mounted on a substrate in substantially the same manner asin Example 1, but a different adhesive was used. Specifically, whenpreparing the adhesive mentioned above, no electrically conductingparticles were added. Also in this case, the electrodes of theindividual chips could be satisfactorily connected to the correspondingelectrodes on the substrate. Presumably this is because the bumps of thechips and the connection electrodes of the glass epoxy substrate werebrought into direct contact with each other and were firmly bondedtogether by the adhesive.

Example 7

IC chips were mounted on a substrate in substantially the same manner asin Example 1, but an intermediate inspection step was additionallyprovided to inspect the electrical connection between the electrodesafter the adhesive-coated chips were obtained. First, theadhesive-coated chips using the adhesive obtained according to Example 6were heated at 150° C. under 20 kgf/mm², and upon lapse of 2 seconds,the connection resistance at individual connection points was measuredusing a multimeter while the chips were kept under pressure. Similaradhesive-coated chips were connected at 150° C. under 20 kgf/mm² for 4seconds, and then the substrate was removed from the connectingapparatus. Since in this stage the adhesive had started to set due toapplication of heat and pressure, the individual IC chips weretemporarily fixed on the substrates. These substrates were inspectedwith no pressure applied thereto, and had one defective IC chip each.

The defective IC chips were mechanically peeled off and new chips wereconnected in the aforementioned manner; in this case, the chips could besatisfactorily connected. In both cases, since the adhesives were notsufficiently set, the peeling of the chips and the subsequent cleaningoperation using a solvent could be performed very easily, facilitatingthe repair work. Using the DSC, the rates of reaction of the adhesiveswere measured in terms of heat quantity, and were found to be 7% in theformer case and 20% in the latter.

After the connection inspection step and the repair step describedabove, the IC chips were connected at 150° C. under 20 kgf/mm² for 15seconds, and they showed good connection characteristics in both cases.After the adhesive sets, it is extremely difficult to peel off the chipsand clean the substrate by using a solvent, but according to thisexample, repair work could be performed with ease though numerous chipswere mounted on a small-sized substrate.

Example 8

IC chips were mounted on a substrate by a method similar to thatemployed in Example 1, but static pressure was utilized in the step ofapplying heat and pressure at the time of connection.

Specifically, adhesive-coated chips were placed on a glass epoxysubstrate, and after the electrodes were positioned relative to eachother using a CCD camera, the substrate having the chips temporarilyfixed thereon was set in a pressure pot for pneumatic pressure treatmentat 120° C. under 20 kg/cm² for 30 minutes, then cooled to roomtemperature, and removed from the pressure pot. According to thisexample, since the individual chips can be applied with uniform pressureregardless of their heights, it is unnecessary to use a buffering memberunlike Example 1. Also, it is possible to treat a large number of MCM ata time depending on the capacity of the pressure pot.

Example 9

IC chips were mounted on a substrate in substantially the same manner asin Example 1, but a polytetrafluoroethylene film (thickness: 80 μm) wasused as the separator. The obtained MCM was evaluated in the same manneras in Example 1, and it was found that the adhesive could be transferredto the surfaces of the chips in more exact shape matching the chip sizeespecially at the edges. Presumably this is because the separator wasmore flexible than that used in Example 1 and thus the adhesive could becut sharply along the edges of the chips. The elasticity modulus of thepolyethylene terephthalate film was 200 kgf/mm², while the elasticitymodulus of the polytetrafluoroethylene film was 40 kgf/mm².

Example 10

IC chips were mounted on a substrate in substantially the same manner asin Example 1, but the adhesive-coated chips were produced with asilicone rubber sheet of 0.5 mm thick interposed between the separatorand the surface plate. In this case, the adhesive could be transferredto the surfaces of the chips in more exact shape matching the chip sizethan in Example 1, especially at the edges. This is presumably becausethe silicone rubber sheet served as a cushioning member. Also in thecase where a soft rubber layer exists under the separator, the thicknessof the adhesive layer formed on the electrode surface is controlled bythe heights of the bumps and the electrically conducting particles;therefore, the bumps each had an adhesive layer of about 4 μm thickformed thereon and the region other than the bumps had an adhesive layerof about 20 μm thick formed thereon, which thickness is identical to theoriginal thickness.

Comparative Example

Following the method of mounting IC chips on a substrate employed inExample 1, the adhesive film with the separator was cut into piecescorresponding in shape to respective chip sizes, and the cut pieces wereaffixed to the respective electrode surfaces. Since the chips weresmall, it took much time to affix the cut pieces accurately to thechips. More than twenty minutes were required to obtain one MCM, andthus the efficiency was low compared with Example 1 in which one MCMcould be produced within one minute.

As is clear from the above description of the examples and thecomparative example, according to the present invention, the adhesivelayer can be formed accurately on the electrode surfaces of individualchips with different sizes, and also multiple chips of different sizescan be mounted at a time, whereby MCM can be fabricated with highefficiency.

What is claimed is:
 1. An apparatus comprising: a connection sheetincluding a separator layer and an adhesive film layer formed on saidseparator layer such that said adhesive film layer can be peeled fromsaid separator layer, wherein a cohesive strength of said adhesive filmlayer is decreased when said adhesive film layer is heated to apredetermined temperature; and a plurality of electronic parts, each ofsaid electronic parts having an electrode surface and at least oneelectrode on said electrode surface, said electrode surface of each ofsaid electronic parts affixed to said adhesive film layer such that saidadhesive film layer coats all exposed portions of said electrode surfaceand coats all exposed surfaces of said at least one electrode, whereinsaid cohesive strength of said adhesive film layer is such that whensaid adhesive film layer is heated to the predetermined temperature,only a portion of said adhesive film layer immediately surrounding eachof said electronic parts will be peeled from said separator layer whensaid each of said electronic parts is removed from said adhesive filmlayer.
 2. The apparatus of claim 1, wherein said adhesive film layerincludes electrically conductive particles.
 3. The apparatus of claim 2,wherein each of said electrically-conductive particles has a length in arange of 1 μm to 7 μm.
 4. The apparatus of claim 1, wherein a viscosityof said adhesive film layer is no greater than 1000 poises.
 5. Theapparatus of claim 4, wherein said viscosity of said adhesive film layeris in a range of 10 poises to 100 poises.
 6. The apparatus of claim 1,wherein said adhesive film layer includes a hardener material.
 7. Theapparatus of claim 6, wherein said hardener material includes at leastone of imidazole, hydrazide, boron trifluoride-amine complex,amine-imide, polyamine salt, onium salt, and dicyandiamide.
 8. Theapparatus of claim 6, wherein said hardener material has an activationtemperature in a range of 40° to 200° C.
 9. An apparatus comprising: aconnection sheet including a separator layer and an adhesive film layerformed on said separator layer such that said adhesive film layer can bepeeled from said separator layer; and a plurality of electronic partsarranged on said adhesive film layer such that an electrode surface ofeach of said electronic parts is affixed to said adhesive film layer;wherein said adhesive film layer has a cohesive strength sufficient tohold and retain each of said electronic parts when a temperature of saidadhesive film layer is below 40° C., and sufficient to release each ofsaid electronic parts when a temperature of said adhesive film layer isat or above 40° C., wherein said cohesive strength of said adhesive filmlayer is such that when said adhesive film layer is heated to atemperature at or above 40°, only a portion of said adhesive film layerimmediately surrounding each of said electronic parts will be peeledfrom said separator layer when said each of said electronic parts isremoved from said adhesive film layer.
 10. The apparatus of claim 9,wherein said adhesive film layer includes electrically-conductiveparticles.
 11. The apparatus of claim 10, wherein each of saidelectrically-conductive particles has a length in a range of 1 μm to 7μm.
 12. The apparatus of claim 9, wherein a viscosity of said adhesivefilm layer is no greater than 1000 poises.
 13. The apparatus of claim12, wherein said viscosity of said adhesive film layer is in a range of10 poises to 100 poises.
 14. The apparatus of claim 9, wherein saidadhesive film layer includes a hardener material.
 15. The apparatus ofclaim 14, wherein said hardener material includes at least one ofimidazole, hydrazide, boron trifluoride-amine complex, amine-imide,polyamine salt, onium salt, and dicyandiamide.
 16. The apparatus ofclaim 14, wherein said hardener material has an activation temperaturein a range of 40° to 200° C.